Intrinsic and extrinsic factors driving leukaemogenesis

The purpose of this thesis is to better understand how certain intrinsic and extrinsic factors contribute to the progression of leukaemia. For this reason, we focused on the study of two different genes (intrinsic factors) namely SLIT2 and MLL5 and on macrophages found in the bone marrow microenvironment (extrinsic factor). High expression of SLIT2 and MLL5 was associated with a better clinical outcome. In vitro and in vivo, we showed that low SLIT2 levels lead to increased leukaemic cell proliferation, while high levels of MLL5 improve the response to the differentiation agent all-trans retinoic acid. Additionally, we show that the emergence of leukaemia is associated with an increased frequency of immunosuppressive M2 macrophages. Patients with high M2 macrophages are linked to a worse clinical outcome. The interaction between leukaemic cells and M2 macrophages leads to increased engraftment in vivo and a more aggressive course of the disease. Furthermore, M2 macrophages lead to improved homing and resistance against phagocytosis, while also driving a more OXPHOS-like metabolism. The latter was also confirmed by single-cell analysis showing increased Fatty Acid Oxidation and NAD+ generation in AML-associated macrophages, which could be targeted therapeutically

Inhibition of the succinyl dehydrogenase complex in acute myeloid leukemia leads to a lactate-fuelled respiratory metabolic vulnerability

Metabolic programs can differ substantially across genetically distinct subtypes of acute myeloid leukemia (AML). These programs are not static entities but can change swiftly as a consequence of extracellular changes or in response to pathway-inhibiting drugs. Here, we uncover that AML patients with FLT3 internal tandem duplications (FLT3-ITD+) are characterized by a high expression of succinate-CoA ligases and high activity of mitochondrial electron transport chain (ETC) complex II, thereby driving high mitochondrial respiration activity linked to the Krebs cycle. While inhibition of ETC complex II enhances apoptosis in FLT3-ITD+ AML, cells also quickly adapt by importing lactate from the extracellular microenvironment. 13C3-labelled lactate metabolic flux analyses reveal that AML cells use lactate as a fuel for mitochondrial respiration. Inhibition of lactate transport by blocking Monocarboxylic Acid Transporter 1 (MCT1) strongly enhances sensitivity to ETC complex II inhibition in vitro as well as in vivo. Our study highlights a metabolic adaptability of cancer cells that can be exploited therapeutically.</p

Prognostic implications of the ID1 expression in acute myeloid leukemia patients treated in a resource-constrained setting

Introduction: The aberrant expression of the inhibitor of DNA binding (ID1) gene has been frequently associated with the leukemogenesis and prognostication acute myeloid leukemia (AML), although its clinical importance has never been investigated in patients treated outside well-controlled clinical trials. Methods: Using quantitative real-time polymerase chain reaction, we investigated the role of the ID1 expression in the clinical outcomes of non-selected patients with acute myeloid leukemia treated in a real-life setting. Results: Overall, 128 patients were enrolled. Patients with high ID1 expression had a lower 3-year overall survival (OS) rate of 9%, with the 95% confidence interval (95%CI) at 3 to 20%, compared to patients with a low ID1 expression (22%, 95%CI: 11 - 34%) (p = 0.037), although these findings did not retain significance after adjustment (hazard ratio (HR): 1.5, 95%CI: 0.98 - 2.28; p = 0.057). The ID1 expression had no impact on post-induction outcomes (disease-free survival, p = 0.648; cumulative incidence of relapse, p = 0.584). Conclusions: Although we are aware thar our data are confronted with many variables that cannot be fully controlled, including drug unavailability, risk-adapted treatment, comorbidities and the time from diagnosis to treatment initiation, we are firm believers that such an initiative can provide more realistic data on understudied populations, in particular those from low- and middle-income countries.</p

The Combination of Gefitinib With ATRA and ATO Induces Myeloid Differentiation in Acute Promyelocytic Leukemia Resistant Cells

In approximately 15% of patients with acute myeloid leukemia (AML), total and phosphorylated EGFR proteins have been reported to be increased compared to healthy CD34(+) samples. However, it is unclear if this subset of patients would benefit from EGFR signaling pharmacological inhibition. Pre-clinical studies on AML cells provided evidence on the pro-differentiation benefits of EGFR inhibitors when combined with ATRA or ATO in vitro. Despite the success of ATRA and ATO in the treatment of patients with acute promyelocytic leukemia (APL), therapy-associated resistance is observed in 5-10% of the cases, pointing to a clear need for new therapeutic strategies for those patients. In this context, the functional role of EGFR tyrosine-kinase inhibitors has never been evaluated in APL. Here, we investigated the EGFR pathway in primary samples along with functional in vitro and in vivo studies using several APL models. We observed that total and phosphorylated EGFR (Tyr992) was expressed in 28% and 19% of blast cells from APL patients, respectively, but not in healthy CD34(+) samples. Interestingly, the expression of the EGF was lower in APL plasma samples than in healthy controls. The EGFR ligand AREG was detected in 29% of APL patients at diagnosis, but not in control samples. In vitro, treatment with the EGFR inhibitor gefitinib (ZD1839) reduced cell proliferation and survival of NB4 (ATRA-sensitive) and NB4-R2 (ATRA-resistant) cells. Moreover, the combination of gefitinib with ATRA and ATO promoted myeloid cell differentiation in ATRA- and ATO-resistant APL cells. In vivo, the combination of gefitinib and ATRA prolonged survival compared to gefitinib- or vehicle-treated leukemic mice in a syngeneic transplantation model, while the gain in survival did not reach statistical difference compared to treatment with ATRA alone. Our results suggest that gefitinib is a potential adjuvant agent that can mitigate ATRA and ATO resistance in APL cells. Therefore, our data indicate that repurposing FDA-approved tyrosine-kinase inhibitors could provide new perspectives into combination therapy to overcome drug resistance in APL patients

Um microambiente de macrófagos polarizados em M2 impulsiona a leucemogênese e o mau prognóstico na leucemia mielóide aguda

While it is increasingly becoming clear that cancers are a symbiosis of diverse cell types and tumor clones, the tumor supportive microenvironment (TSM) in acute myeloid leukemias (AML) remains poorly understood. Here, we uncover that patients with the poorest prognosis harbor an M2-polarized macrophage compartment. Coculture of leukemic blasts on M2 macrophages promotes cell survival and drug resistance. Intrabone marrow co-injection of M2- macrophages induces fatal leukemia of acute promyelocytic leukemia blasts, which are otherwise poor grafters. Even a short-term two-day in vitro exposure to M2 macrophages can \"train\" leukemic blasts after which cells are protected against phagocytosis, display increased mitochondrial metabolism and in vivo homing, resulting in full-blown leukemia. We developed an M2-based biomarker panel that outperforms currently used AML prognosis predictors. Our study provides insight into the mechanisms by which the TSM contributes to aggressive leukemia development and provides alternatives for effective targeting strategies.Embora esteja cada vez mais claro que os cânceres são uma simbiose de diversos tipos celulares e clones tumorais, o microambiente de suporte tumoral (MST) em leucemias mieloides agudas (LMA) ainda permanece pouco compreendido. Nesse trabalho, nos demonstramos que os pacientes com pior prognóstico contem um compartimento de macrófagos polarizados em M2. A co-cultura de blastos leucêmicos com macrófagos M2 promoveu a sobrevivência celular e a resistência a agentes quimioterapicos. A injeção de macrófagos M2 na medula induziu leucemia fatal em animais transplantados com blastos de leucemia promielocitica aguda, usualmente conhecidos por seu baixo potencial de enxertia. Mesmo a exposição in vitro por dois dias a macrófagos M2, conseguiu \"treinar\" os blastos leucêmicos, após os quais as células são protegidas contra a fagocitose, apresentam metabolismo mitocondrial e homing in vivo aumentado, resultando em leucemia desenvolvida. Nós desenvolvemos um painel de biomarcadores baseado em macrofagos M2 que supera os preditores de prognóstico para LMA usados atualmente. Nosso estudo fornece uma visão sobre os mecanismos pelos quais o MST contribui para o desenvolvimento de leucemia agressiva e fornece alternativas para estratégias eficazes de tratamento e manejo clinico

High ME1 Expression Is a Molecular Predictor of Post-Transplant Survival of Patients with Acute Myeloid Leukemia

Several laboratory and clinical variables have been reported to be associated with the outcome of intensive chemotherapy for acute myeloid leukemia (AML), but only a few have been tested in the context of hematopoietic stem cell transplant (HSCT). This study aimed to identify genes whose expression of AML at diagnosis were associated with survival after HSCT. For this purpose, three publicly available adult AML cohorts (TCGA, BeatAML, and HOVON), whose patients were treated with intensive chemotherapy and then subjected to allogeneic or autologous HSCT, were included in this study. After whole transcriptome analysis, we identified ME1 as the only gene whose high expression was associated with shorter survival in patients subjected to HSCT. In addition, the inclusion of ME1 expression was able to improve the European LeukemiaNet risk stratification. Pathways related to lipid biosynthesis, mainly fatty acids, and cholesterol were positively correlated with ME1 expression. Furthermore, ME1 expression was associated with an M2 macrophage-enriched microenvironment, mature AML blasts hierarchy, and oxidative phosphorylation metabolism. Therefore, ME1 expression can be used as biomarker of poor response to HSCT in AML

High ME1 Expression Is a Molecular Predictor of Post-Transplant Survival of Patients with Acute Myeloid Leukemia

Several laboratory and clinical variables have been reported to be associated with the outcome of intensive chemotherapy for acute myeloid leukemia (AML), but only a few have been tested in the context of hematopoietic stem cell transplant (HSCT). This study aimed to identify genes whose expression of AML at diagnosis were associated with survival after HSCT. For this purpose, three publicly available adult AML cohorts (TCGA, BeatAML, and HOVON), whose patients were treated with intensive chemotherapy and then subjected to allogeneic or autologous HSCT, were included in this study. After whole transcriptome analysis, we identified ME1 as the only gene whose high expression was associated with shorter survival in patients subjected to HSCT. In addition, the inclusion of ME1 expression was able to improve the European LeukemiaNet risk stratification. Pathways related to lipid biosynthesis, mainly fatty acids, and cholesterol were positively correlated with ME1 expression. Furthermore, ME1 expression was associated with an M2 macrophage-enriched microenvironment, mature AML blasts hierarchy, and oxidative phosphorylation metabolism. Therefore, ME1 expression can be used as biomarker of poor response to HSCT in AML